The aim of this project is to characterize the endocrine mechanism regulating calcium metabolism during pregnancy and the perinatal period in human and non-human primates. Total and ionized calcium, magnesium, phosphorus, and albumin, as well as the calcium-regulating hormones PTH and CT, are measured in maternal, fetal, and neonatal blood under baseline conditions and following provocative stimuli. Work completed thus far indicates that pregnancy is associated with decreasing total calcium, but not minimal change in ionized calcium levels, increasing PTH secretion, and probably no significant change in CT values. The primate fetus responds appropriately with PTH release to hypocalcemia and CT release to hypercalcemia and glucagon. During the coming year it is planned to continue longitudinal studies in human pregnancy, institute examination of relationships in cord blood, and complete monkey studies of perinatal response. BIBLIOGRAPHIC REFERENCES: Calcium metabolism during the menstrual cycle (abstract) Gynecol. Invest. 8:60, 1977, Pitkin, R.M., Reynolds, W.A., Williams, G.A., Hargis, G.K., and Kawahara, W. Magnesium sulfate: Metabolic effects in mother and infant (abstract) Gynecol. Invest. 8:76, 1977, Cruikshank, D.P., Pitkin, R.M., Reynolds, W.A., Williams, G.A., and Hargis, G.K.